Quantum Theory
- This theory replace Bohr because his nergy levels only worked for hydrogen
-The quantum theory uses complex mathematical equations to decrible waves
- The model predicts quantized energy levels of electrons. It depends on the probility of finding an electrons in a certain position
-This is categorized the 7 energy levels into 4 orbits
Orbitals
- An area where an electron can be found
- There are 4 orbitals; s,p,d, f
- The orbitals are filled based on the location of the electrons on the periodic tables
S-Orbitals
- Given a 3-d figure, the s-orbital would look like a sphere
- It can hold a max of 2 electrons-one pair of electrons
- S-orbitals will occur in all 7 energy levels
P-orbitals
- Electrons begin filling the p-orbitals in the 2nd energy level after filling the 2s-orbital
- It can hold a total of 6 electron-3 electron pairs
- The shape of each of the p-orbitals look like a dumbbell
D-orbitals
- The electrons begin filling the d-orbitals in the 3rd energy level,after filling the 4s orbital
-The orbitals will hold 10 electrons-5 electron pairs
- The 3-d shape of the d-orbital is a 4 x-shapes with a life-saver around the center
F-orbitals
- They occur in the 4th energy level after filling the 6s orbital
- The f-orbitals can hold 14 electrons- 7 electron pairs
- The electrons are in such chaos that there is no set shape to describe them
Electron Configurations
-A visual way to write how the electrons fill the orbitals.
-The orbitals fill as you flow left-right and top to bottom on the periodic table:1s,2s,
-Example with directions
-Find out how many electrons are in the Manganese. 25 electrons
- Flow left --> right and top --> bottom filling the orbitals:
- 1s,2s,2p,
-Self-check- add all of the superscripts; that total should match the number of electrons
Practice: Write the electron configuration
1. Electron configuration of nitrogen
answer: 1s^2,2s^2,2p^3
2. Electron configuration of Bromine(Br)
answer:1s^2 2s^2 2p^6 3s^2 3p^6 4s^2 3d^10 4p^5
3. Cerium (Ce)
Use of the Bohr Model
While Bohr's model only worked for the hydrogen atom, his energy ideas are still used today
Electrons are in the energy levels and can move energy levels when the electrons become energized (quantized)
Energy levels of an atom
Bohr proposed the electrons can only reside in an energy level
The lowest level is closest to the nucleus Ground State- When electrons are in the lowest possible level Quantum- amount of energy needed to jump energy levels (particular energies given) Excited State- when an electron has been quantized(given particular energy)- leads to waves of light
Calculations
E=hc/l, v=c/ l
E=energy (eV) or (Joules)
h=6.63 x 10-34 joules/hertz
c=3.0 x 108 m/s
v= frequency (Hz = 1/sec)
Trends of the Periodic Table
When studying the periodic table one can tell many things about an element just by its location.These trends help scientists idenify new elements and understand why an element has different properties.
Atomic Radius
- Atomic radius within a group increases as one moves vertically down the periodic table
-Atomic radius within the period decreases as one moves horizontally right across the periodic table
Ionization Energy
(the energy required to remove an electron from an element)
- The energy required for elements within a group decreases as one moves vertically down the periodic table
- The energy required for elements within a period increases as one moves horizontally right across the periodic table
Shielding Effect
-A decrease in the attraction of the outer electrons (valence electrons) to the positively-charged nucleus
- Increases as one moves vertically down the periodic table
- It remains constant as you move right across the periodic table because the electrons aren't being added to a new energy level
Electronegativity (EN)
- How strong the bonds are within the compound
- Decreases as you move down the periodic able because the energy levels are growing
- Increases as you move right across the periodic a table because more p+ are added to the nucleus allowing for more electrons
F is the most electronegative element at 4.0 and Francium is the least at 0.7 (Noble gases are excluded)
Wlectron affinity
- A measure of the energy change that occurs as an electron is added to an atom
- Has the same trends as electronegativity for the same reasons (Last Slide)
Atomic Mass Number(Mass Number)
The average of alll of the masses of the naturally occurring isotopes of an element
The mass number is the rounded atomic mass. It is the number of protons and neutrons found in an atom
Atomic mass is expressed in Atomic Mass Units(amu)
- The mass numberis the mass of both the protons and the neutrons, nt the total mass
- Scientist developed a unit to compare all atoms
- 1 amu=1.66 x 10^-24 g (1/12th the mass of the carbon-12)
Average Atomic Mass on the PT
-When you read the mass on the PT, the unit are amu
- Cu= 63.55 amu
- These average atomic masses are the average of the atomic masses of the isotopes occurring in nature
- Amu when single atom; grams when larger amounts of materials
How to calculate the amu
- Scientist use the % of the existence of an isotopes multiplied by the mass of all totaled to get th mass
ex) Cu-exists 69.17% of the time yielding a mass of 62.94 amu and Cu- 65 exists the other 30.38% of the time with a mass of 64.93 amu. Together hey create the amu of Cu.
(.6917 x 62.94 amu) + (.3083 x 64.93 amu)
=63.55 amu
Valence electrons : # in the s+p orbitals in that period, skip d/f orbitals: same group of elements have the same # of valence electrons; group # = valence electrons ; max of 8 electrons(v); Hydrogen and Helium are exception to Octet (only total 2)
Ion- an element that has donated or taken electrons
Cations- left hand side
Groups I,II,III
sometimes (IV)
gives away electrons
Ca+2: Calcium ion
Anions- Right hand side of periodic table
sometimes(IV)
Groups V,VI,VIII
taking in electrons
O-2: oxide ion
Ionic Bonds
-Oppositely charged ions attract and bond to eacg other. The compounds become know as salts.
- Ex: Te attraction of a Na +1 ion to a Cl ion forms the compound commonly know as table salt
Writing Ionic Formulas
- Write the cation and anion from the name: Lithium oxide: Li+1 O-2
- Switch the charges to become subscripts: Li
-Reduce if like charges or common multiples (+2,-2 becomes 1:1, +4,-2 becomes 2:1)
Determining formulas mathematically
Percent Composition
- Calculating the percent that an element eists within a compound
- Essentially you are giving each element a grade on its participation within the compound
Samples
1. Mass of elements
a. H: 2*1.01= 2.02 g
b. O: 1*15.99= 15.99 g
2. Mass of compounds
2.02 + 15.99 = 18.01 g
3a. Percent H: 202/18.01 = .112*100= 11.2 %
3b. Percent O: 15.99/
Calculating the % of an element
- If we recover 12.31 g after distillation, how many g of O are present?
Working from % to formula
- We can also work backwards to determine the formula of a compound. This is called the empirical formula. It gives the lowest whole-number ratio
Step by step
-When given a problem assume that you have 100 h total( like %, make it easy)25.4%=25.4 g
-Calculate the moles of each element
-Divide the moles of each element by the smallest mole number to get the ratio.(Round to the nearest .5)
-Multiply ratio by 2 if you have a .5 ratio
- Write the formula using the whole number ratio
Sample
A cmpd is analzd and found to contain 25.9 % N and 74.1 % O.What is the empirical formula?
25.9g N x (1molN/14.0 g)=1.85 mol N
74.1 g O x (1mol/ 15.99 g) = 4.63 mol O
Ratio: 1.85/1.85 : 4.63/1.85 = 1:2.5
Whole Number: 2(1:2.5)= 2.5
Formula N2O5
Hydrates
- Compuonds that have have water trapped in them
- The water is trapped during a cooling process
- Formula: CuSO^4 * 5H^2 0
- Naming: Copper II sulfate pentahydrate
% composition of h20
-You find the total atomic mass of the compond( all of the elements and water)
- Take the mass of the water/total mass x 100%
sample
- BaCl2 x 2H20
-Ba: 137.3 g
- Cl: 2 x 35.45 = 70.90 g
- H2O: 2 x 18.01= 36.02 g
- Total: 244.2 g
- % H20= (36.02/244.2)x 100= 14.75%
Empirical Formula w/ hydrates
- treat the compound as one thing and water as another
- Complete the same step by step problems as before
- Grams-->moles-->mole:mole ratio-->formula answer
Sample
10.407 g of hydrated barium iodide is heated and .877 g of H2O is driven off. Assuming this is all of the water, what is it's formula and name?
Naming Covalent bonds
1) Elements are listed by lower group first
2) If both elements ar in the same group, the lower atomic number element is the first of the bond
3) 2nd element will end with -ide
4) Prefixes are used to tell how many atoms are in the bond(mono, bi, tri, etc)
5) first element will only have a prefix if it is more than one
Examples
BF3- Boron trifluoride
Dinitrogen pentaoxide-N2O5
Chemical Reactions
-Chemical reactions occur when bonds between the outermost part of the atoms are formed or broken
- Chemical reactions involve changes in matter, the mking of new materials with new properties, and energy changes
- Symbols represents elements, formulas describe compounds, chemical equations describe a chemical reaction
Chemical equations
Their job: Depict the kind of reactants and products and their relative amounts in a reaction
4 Al + 02 =Al2 O3
The numbers in the front are called stoichiometric coefficients
The letters s,g, and l are the physical sates of the compounds
Parts of the Reaction Equation
- A= sign separtes molecules on the same side
- The arrow is read as yields
- Example
C+ O -> CO2
- This reads " carbon plus oxygen reacts to yield carbon dioxide"
Why?
- Because of the principle of the conservation of matter, an equation musr be balanced
- It must have the same number of atoms of the same kind on both sides
Symbols
-Solid(s)
- Liquid(l)
- Gas(g)
- Aqueous sloution(aq)
- Catalyst
- Escaping gas(^)
- change of temperature(triangle)
Balancing Equations
- When balancing a chemical reaction you may add coefficients in front of the compounds to balance the reaction, but you may NOT change the subscript
- Changing the subscripts changes the compound. Subscripts are determined by the valence electrons( charges for ionic or sharing for covalent)
Steps to Balancing Equations
1) Write the correct formula for the reactants and the products
2) Find the number of atoms for each element on the left side. Compare those against the number of the atoms of the same elment on the right side
3) Determine where to place coefficients in front of formulas so that the left side has the same number of atoms as the right side for EACH each element in order to balance equation
4) Check your answer to see if:
- the number of atoms on both sides of the equation are now balanced
- the coefficients are in the lowest possible whole ratios. (reduced)
Some Suggestions to help you
- Take one element at a time, working left to right except for H and O. Save H for next to last and O last
- IF everything balances except for O and there is no way to balance O with a whole number, double all the coefficients and try again. (because O is diatomic as an element)
- (Shortcut) Polyatomic ions that appear on both sides of the equation should be balanced as independent units
Stiochiometry
Review
if you have 34.1 g of CuSO4, how many moles of CuSO4 do you have? How many molecules do you have? Write in Sig Figs.
Conservation of Mass
The total mass remains constant when comparing reactants and products(the two will be equal)
The total mass of hydrogen and iodine will equal the mass of hydrogen iodine.
Writing Mole Ratios
This uss the coefficients of a balanced equation to show the relationship between compounds.
N2 (g) + 3H2 --> 2 NH3 (g)
what this means: 1 mol N2: 2 mol NH3 : 3 mol H2
Mole à Mole calculations
How many moles of NH3 are produced when 0.60 mol of nitrogen reacts with hydrogen? N2 + 3H2 à NH3 (g)
.60 mol N2 x 2 mol NH3/ 1 mol N2
Other conversions
1) When asked for L at STP use: 22.4 L/1 mol
2) When given molarity (M) remember to keep the # with moles (6 mol/L= 6M)
3) 1 mol/6.022 x 1023 molecules
4) Density (g/ml)
Steps
1) Balance he equation
2) Start with the given number
3) Covert to moles
4) Use the mole: mole ratio from the balanced equation
5) Covert to the required unit using one of the conversion factors
Limited and Excess Reagents
In a chemical reaction, one compound drives how long and how much a reaction can occur. Limiting- determines how much product can be formed Excess- Some left over during the reaction process
Using the information
If we have 30 pairs of shoes and 25 people, how many people can have shoes?
How to do the problem
- Convert the grams of each reactant into moles of the product
- The smaller mole value tells you which starting reactant is the limiting reactant
- Use the moles of the limiting reagent to calculate the amount of products
Excess Leftover
Select one product that you formed
Convert that product into grams of excess reactant
Subtract those grams from the starting grams = how much is leftover
- Mathematical calculation of how “good” your lab results are
- % yield = actual yield x 100%
- Theoretical yield
- Actual yield- results from lab
- Theoretical yield- amount predicted from calculations
Gas Laws- Unit 9
Elements that exist as gases at 25 degrees C and 1 atmosphere- H, He, N, O, F, Ne, Cl, Ar, Kr, Xe, Rn
Physical characteristics
- Gases assume the volume and shape of their matter
- Gases are the most compressible state of matter
- Gases will mix evenly and completely when confined to the same container
- Gases have much lower densities than liquids and solids
Variation of gas volume with temperature at constant pressure
V a T
V = constant x T
V1/T1 = V2/T2
Temperature must be in Kelvin
T(K) = t(° C) + 273.15
Ideal Gas Equation
PV= nRT
R is a the gas constant
Used when we are discussing a single gas in a non-changing environment
The conditions 0 C and 1 atm are called standard temperature and pressure (STP)
Experiments show that at STP, 1 mole of an ideal gas occpies 22.414 L
R = PV= (1 atm)(22.414L)
nT (1 mol)(273.15K)
Dalton’s law of Partial Pressures
V and T stay constant
P1 + P2 = P total
Colligative properties
-Molality (m)- mol of solute/kg solvent
Boiling point elevation
DT= T (final)- T (intial) DT(b) = bp(solution)- bp (pure solvent) DT(b) = k(b) x m
Where k(b) à boiling point elevation constant DT b(solution) = DT b(solvent) + D T
Freezing point depression
DT= T final – T initial D Tf = fp pure solvent – fp solution D Tf = kf x m
where kf à freezing point depression constant
T f(solution) = Tf(solvent) = D T
Concept
The freezing point of water is lowered proportional to the number of solute species present
Why is it better to leave the anti-freeze in your cooling system
Temp. and Solubility
-Conversely a gas will be less soluble at a higher temperature
-This is because when gas molecules are moving faster they are able to escape from the liquid surface
Quantum Theory
- This theory replace Bohr because his nergy levels only worked for hydrogen
-The quantum theory uses complex mathematical equations to decrible waves
- The model predicts quantized energy levels of electrons. It depends on the probility of finding an electrons in a certain position
-This is categorized the 7 energy levels into 4 orbits
Orbitals
- An area where an electron can be found
- There are 4 orbitals; s,p,d, f
- The orbitals are filled based on the location of the electrons on the periodic tables
S-Orbitals
- Given a 3-d figure, the s-orbital would look like a sphere
- It can hold a max of 2 electrons-one pair of electrons
- S-orbitals will occur in all 7 energy levels
P-orbitals
- Electrons begin filling the p-orbitals in the 2nd energy level after filling the 2s-orbital
- It can hold a total of 6 electron-3 electron pairs
- The shape of each of the p-orbitals look like a dumbbell
D-orbitals
- The electrons begin filling the d-orbitals in the 3rd energy level,after filling the 4s orbital
-The orbitals will hold 10 electrons-5 electron pairs
- The 3-d shape of the d-orbital is a 4 x-shapes with a life-saver around the center
F-orbitals
- They occur in the 4th energy level after filling the 6s orbital
- The f-orbitals can hold 14 electrons- 7 electron pairs
- The electrons are in such chaos that there is no set shape to describe them
Electron Configurations
-A visual way to write how the electrons fill the orbitals.
-The orbitals fill as you flow left-right and top to bottom on the periodic table:1s,2s,
-Example with directions
-Find out how many electrons are in the Manganese. 25 electrons
- Flow left --> right and top --> bottom filling the orbitals:
- 1s,2s,2p,
-Self-check- add all of the superscripts; that total should match the number of electrons
Practice: Write the electron configuration
1. Electron configuration of nitrogen
answer: 1s^2,2s^2,2p^3
2. Electron configuration of Bromine(Br)
answer:1s^2 2s^2 2p^6 3s^2 3p^6 4s^2 3d^10 4p^5
3. Cerium (Ce)
Use of the Bohr Model
While Bohr's model only worked for the hydrogen atom, his energy ideas are still used today
Electrons are in the energy levels and can move energy levels when the electrons become energized (quantized)
Energy levels of an atom
Bohr proposed the electrons can only reside in an energy level
The lowest level is closest to the nucleus
Ground State- When electrons are in the lowest possible level
Quantum- amount of energy needed to jump energy levels (particular energies given)
Excited State- when an electron has been quantized(given particular energy)- leads to waves of light
Calculations
E=hc/l, v=c/ l
E=energy (eV) or (Joules)
h=6.63 x 10-34 joules/hertz
c=3.0 x 108 m/s
v= frequency (Hz = 1/sec)
Trends of the Periodic Table
When studying the periodic table one can tell many things about an element just by its location.These trends help scientists idenify new elements and understand why an element has different properties.
Atomic Radius
- Atomic radius within a group increases as one moves vertically down the periodic table
-Atomic radius within the period decreases as one moves horizontally right across the periodic table
Ionization Energy
(the energy required to remove an electron from an element)
- The energy required for elements within a group decreases as one moves vertically down the periodic table
- The energy required for elements within a period increases as one moves horizontally right across the periodic table
Shielding Effect
-A decrease in the attraction of the outer electrons (valence electrons) to the positively-charged nucleus
- Increases as one moves vertically down the periodic table
- It remains constant as you move right across the periodic table because the electrons aren't being added to a new energy level
Electronegativity (EN)
- How strong the bonds are within the compound
- Decreases as you move down the periodic able because the energy levels are growing
- Increases as you move right across the periodic a table because more p+ are added to the nucleus allowing for more electrons
F is the most electronegative element at 4.0 and Francium is the least at 0.7 (Noble gases are excluded)
Wlectron affinity
- A measure of the energy change that occurs as an electron is added to an atom
- Has the same trends as electronegativity for the same reasons (Last Slide)
Atomic Mass Number(Mass Number)
The average of alll of the masses of the naturally occurring isotopes of an element
The mass number is the rounded atomic mass. It is the number of protons and neutrons found in an atom
Atomic mass is expressed in Atomic Mass Units(amu)
- The mass numberis the mass of both the protons and the neutrons, nt the total mass
- Scientist developed a unit to compare all atoms
- 1 amu=1.66 x 10^-24 g (1/12th the mass of the carbon-12)
Average Atomic Mass on the PT
-When you read the mass on the PT, the unit are amu
- Cu= 63.55 amu
- These average atomic masses are the average of the atomic masses of the isotopes occurring in nature
- Amu when single atom; grams when larger amounts of materials
How to calculate the amu
- Scientist use the % of the existence of an isotopes multiplied by the mass of all totaled to get th mass
ex) Cu-exists 69.17% of the time yielding a mass of 62.94 amu and Cu- 65 exists the other 30.38% of the time with a mass of 64.93 amu. Together hey create the amu of Cu.
(.6917 x 62.94 amu) + (.3083 x 64.93 amu)
=63.55 amu
Conversion Factors
- Avagadro's Number: 6.022 x 10^23 atoms/molecules
1mole
- Molar Mass: Atomic mass(g)
1mole
Valence electrons : # in the s+p orbitals in that period, skip d/f orbitals: same group of elements have the same # of valence electrons; group # = valence electrons ; max of 8 electrons(v); Hydrogen and Helium are exception to Octet (only total 2)
Ion- an element that has donated or taken electrons
Cations- left hand side
Groups I,II,III
sometimes (IV)
gives away electrons
Ca+2: Calcium ion
Anions- Right hand side of periodic table
sometimes(IV)
Groups V,VI,VIII
taking in electrons
O-2: oxide ion
Ionic Bonds
-Oppositely charged ions attract and bond to eacg other. The compounds become know as salts.
- Ex: Te attraction of a Na +1 ion to a Cl ion forms the compound commonly know as table salt
Writing Ionic Formulas
- Write the cation and anion from the name: Lithium oxide: Li+1 O-2
- Switch the charges to become subscripts: Li
-Reduce if like charges or common multiples (+2,-2 becomes 1:1, +4,-2 becomes 2:1)
Determining formulas mathematically
Percent Composition
- Calculating the percent that an element eists within a compound
- Essentially you are giving each element a grade on its participation within the compound
Samples
1. Mass of elements
a. H: 2*1.01= 2.02 g
b. O: 1*15.99= 15.99 g
2. Mass of compounds
2.02 + 15.99 = 18.01 g
3a. Percent H: 202/18.01 = .112*100= 11.2 %
3b. Percent O: 15.99/
Calculating the % of an element
- If we recover 12.31 g after distillation, how many g of O are present?
Working from % to formula
- We can also work backwards to determine the formula of a compound. This is called the empirical formula. It gives the lowest whole-number ratio
Step by step
-When given a problem assume that you have 100 h total( like %, make it easy)25.4%=25.4 g
-Calculate the moles of each element
-Divide the moles of each element by the smallest mole number to get the ratio.(Round to the nearest .5)
-Multiply ratio by 2 if you have a .5 ratio
- Write the formula using the whole number ratio
Sample
A cmpd is analzd and found to contain 25.9 % N and 74.1 % O.What is the empirical formula?
25.9g N x (1molN/14.0 g)=1.85 mol N
74.1 g O x (1mol/ 15.99 g) = 4.63 mol O
Ratio: 1.85/1.85 : 4.63/1.85 = 1:2.5
Whole Number: 2(1:2.5)= 2.5
Formula N2O5
Hydrates
- Compuonds that have have water trapped in them
- The water is trapped during a cooling process
- Formula: CuSO^4 * 5H^2 0
- Naming: Copper II sulfate pentahydrate
% composition of h20
-You find the total atomic mass of the compond( all of the elements and water)
- Take the mass of the water/total mass x 100%
sample
- BaCl2 x 2H20
-Ba: 137.3 g
- Cl: 2 x 35.45 = 70.90 g
- H2O: 2 x 18.01= 36.02 g
- Total: 244.2 g
- % H20= (36.02/244.2)x 100= 14.75%
Empirical Formula w/ hydrates
- treat the compound as one thing and water as another
- Complete the same step by step problems as before
- Grams-->moles-->mole:mole ratio-->formula answer
Sample
10.407 g of hydrated barium iodide is heated and .877 g of H2O is driven off. Assuming this is all of the water, what is it's formula and name?
.877gH2Ox(1molH2O/18.01g)= .0493molH2O
10.407-.877= 9.53gBal2
9.53gBal2 x(1mol/391.12g)= .0244mol
.244/.244=1: .0493/.0244=2
Bal2 x 2H2O Barium Iodide Dihydrate
Naming Covalent bonds
1) Elements are listed by lower group first
2) If both elements ar in the same group, the lower atomic number element is the first of the bond
3) 2nd element will end with -ide
4) Prefixes are used to tell how many atoms are in the bond(mono, bi, tri, etc)
5) first element will only have a prefix if it is more than one
Examples
BF3- Boron trifluoride
Dinitrogen pentaoxide-N2O5
Chemical Reactions
-Chemical reactions occur when bonds between the outermost part of the atoms are formed or broken
- Chemical reactions involve changes in matter, the mking of new materials with new properties, and energy changes
- Symbols represents elements, formulas describe compounds, chemical equations describe a chemical reaction
Chemical equations
Their job: Depict the kind of reactants and products and their relative amounts in a reaction
4 Al + 02 =Al2 O3
The numbers in the front are called stoichiometric coefficients
The letters s,g, and l are the physical sates of the compounds
Parts of the Reaction Equation
- A= sign separtes molecules on the same side
- The arrow is read as yields
- Example
C+ O -> CO2
- This reads " carbon plus oxygen reacts to yield carbon dioxide"
Why?
- Because of the principle of the conservation of matter, an equation musr be balanced
- It must have the same number of atoms of the same kind on both sides
Symbols
-Solid(s)
- Liquid(l)
- Gas(g)
- Aqueous sloution(aq)
- Catalyst
- Escaping gas(^)
- change of temperature(triangle)
Balancing Equations
- When balancing a chemical reaction you may add coefficients in front of the compounds to balance the reaction, but you may NOT change the subscript
- Changing the subscripts changes the compound. Subscripts are determined by the valence electrons( charges for ionic or sharing for covalent)
Steps to Balancing Equations
1) Write the correct formula for the reactants and the products
2) Find the number of atoms for each element on the left side. Compare those against the number of the atoms of the same elment on the right side
3) Determine where to place coefficients in front of formulas so that the left side has the same number of atoms as the right side for EACH each element in order to balance equation
4) Check your answer to see if:
- the number of atoms on both sides of the equation are now balanced
- the coefficients are in the lowest possible whole ratios. (reduced)
Some Suggestions to help you
- Take one element at a time, working left to right except for H and O. Save H for next to last and O last
- IF everything balances except for O and there is no way to balance O with a whole number, double all the coefficients and try again. (because O is diatomic as an element)
- (Shortcut) Polyatomic ions that appear on both sides of the equation should be balanced as independent units
Stiochiometry
Review
if you have 34.1 g of CuSO4, how many moles of CuSO4 do you have? How many molecules do you have? Write in Sig Figs.
Conservation of Mass
The total mass remains constant when comparing reactants and products(the two will be equal)
The total mass of hydrogen and iodine will equal the mass of hydrogen iodine.
Writing Mole Ratios
This uss the coefficients of a balanced equation to show the relationship between compounds.
N2 (g) + 3H2 --> 2 NH3 (g)
what this means: 1 mol N2: 2 mol NH3 : 3 mol H2
Mole à Mole calculations
How many moles of NH3 are produced when 0.60 mol of nitrogen reacts with hydrogen? N2 + 3H2 à NH3 (g)
.60 mol N2 x 2 mol NH3/ 1 mol N2
Other conversions
1) When asked for L at STP use: 22.4 L/1 mol
2) When given molarity (M) remember to keep the # with moles (6 mol/L= 6M)
3) 1 mol/6.022 x 1023 molecules
4) Density (g/ml)
Steps
1) Balance he equation
2) Start with the given number
3) Covert to moles
4) Use the mole: mole ratio from the balanced equation
5) Covert to the required unit using one of the conversion factors
Limited and Excess Reagents
In a chemical reaction, one compound drives how long and how much a reaction can occur.
Limiting- determines how much product can be formed
Excess- Some left over during the reaction process
Using the information
If we have 30 pairs of shoes and 25 people, how many people can have shoes?
How to do the problem
- Convert the grams of each reactant into moles of the product
- The smaller mole value tells you which starting reactant is the limiting reactant
- Use the moles of the limiting reagent to calculate the amount of products
Excess Leftover
Select one product that you formed
Convert that product into grams of excess reactant
Subtract those grams from the starting grams = how much is leftover
Percent Yieldfile:///Users/pattersonl14/Desktop/Sugar_Content_in_Beverages-1.doc
- Mathematical calculation of how “good” your lab results are
- % yield = actual yield x 100%
- Theoretical yield
- Actual yield- results from lab
- Theoretical yield- amount predicted from calculations
Gas Laws- Unit 9
Elements that exist as gases at 25 degrees C and 1 atmosphere- H, He, N, O, F, Ne, Cl, Ar, Kr, Xe, Rn
Physical characteristics
- Gases assume the volume and shape of their matter
- Gases are the most compressible state of matter
- Gases will mix evenly and completely when confined to the same container
- Gases have much lower densities than liquids and solids
Pressure = Force
Area
Units of pressure
1 pascal(Pa) = 1 N/m2
1 atm = 760 mmHg = 760 torr
1 atm = 101,325 Pa = 101.325 KPa
Boyles Law
P a 1/V
P1 x V1 = P2 x V2
Content temperature and Content amount of gas
Charles Law
As T increases V increases as well
Variation of gas volume with temperature at constant pressure
V a T
V = constant x T
V1/T1 = V2/T2
Temperature must be in Kelvin
T(K) = t(° C) + 273.15
Ideal Gas Equation
PV= nRT
R is a the gas constant
Used when we are discussing a single gas in a non-changing environment
The conditions 0 C and 1 atm are called standard temperature and pressure (STP)
Experiments show that at STP, 1 mole of an ideal gas occpies 22.414 L
R = PV= (1 atm)(22.414L)
nT (1 mol)(273.15K)
Dalton’s law of Partial Pressures
V and T stay constant
P1 + P2 = P total
Colligative properties
-Molality (m)- mol of solute/kg solvent
Boiling point elevation
DT= T (final)- T (intial)
DT(b) = bp(solution)- bp (pure solvent)
DT(b) = k(b) x m
Where k(b) à boiling point elevation constant
DT b(solution) = DT b(solvent) + D T
Freezing point depression
DT= T final – T initial
D Tf = fp pure solvent – fp solution
D Tf = kf x m
where kf à freezing point depression constant
T f(solution) = Tf(solvent) = D T
Concept
The freezing point of water is lowered proportional to the number of solute species present
Why is it better to leave the anti-freeze in your cooling system
Temp. and Solubility
-Conversely a gas will be less soluble at a higher temperature
-This is because when gas molecules are moving faster they are able to escape from the liquid surface